1. Field of the Invention
This invention relates to a process for the purification of acrylonitrile plant wastewater streams. More particularly, this invention relates to a catalytic process for the eradication of organics and ammonia from such wastewater streams.
2. Description of the Prior Art
Acrylonitrile is one of the highest volume (top fifty) chemicals produced in the U.S. and the world. Nearly all acrylonitrile is produced from propylene, oxygen, and ammonia with either a bismuth phosphomolybdate or an uranium-based compound as catalyst. Acrylonitrile has many uses including for acrylic and modacrylic fibers, ABS and acrylonitrile-styrene copolymers, nitrile rubber, cyanoethylation of cotton and synthetic soil blocks (acrylonitrile polymerized in wood pulp). Acrylonitrile is toxic by inhalation and is a known carcinogen.
Acrylonitrile plants generate a significant volume of wastewater containing organic compounds and ammonia. Methods for treating or disposing these streams include thermal or catalytic incineration, biotreatment, wet oxidation and reduction and deep welling. Currently in the United States, much of the wastewater streams from acrylonitrile plants are disposed of by the deep welling of streams with low levels of contaminants and the incineration of streams with higher levels of impurities. While these disposal methods are believed to be sound and represent general industry practice, producers of acrylonitrile are studying alternative methods of wastewater handling which pose little or no impact on the environment. Biotreatement is often viewed as the future alternative form of treatment of acrylonitrile plant wastewater streams. However, biotreatment is a very expensive alternative and may not be able to satisfactorily remove all impurities from such streams.
A goal of the instant invention is a process for the eradication of organic constituents and other impurities of acrylonitrile plant wastewater streams, which is more environmentally acceptable than deep welling or incineration and more economical than biotreatment.